io2 Elements of Mineralogy. 



It fometimes contains alfo quartz and pyrites. 

 Its fpecific gravity exceeds 3,000. 



III. VARIETY. 



White Clay mixed 'with Mica and Quartz, and 

 of no particular texture. Greifl, of the 

 Germans, or Growan of the Corni/b Miners. 



When the texture is lamellar and the ftone 

 harder, it is called Gneifs. 



IV. VARIETY. 

 Sand/lone mixed 'with Mica, and Feltfpar. 



SPECIES VI. 



Compounds of the Argillaceous with t*wo or 

 more Genera. 



L VARIETY. 

 Micaceous Porphyry. 



This confifts of agreenifh grey, micaceous 

 ground, in which red feltfpar and greenifh 

 foap-rock are inierted. SauJJure Voyage dans 

 les Alpes, p. in," even the mica is not pure, 

 he fufpe&s it contains hornftone, p. 127. 



II. VARIETY. 



Hornjlone mixed with Veins of Spar and Quartz. 



Mentioned by Mr. SauJJure, p. 120, 



CHAP. 



